1. Field of the Invention
The present invention relates to an ink jet printer which supplies ink from an ink tank to a print head and enables ink to eject from the nozzle of the print head to perform printing and an air purging control method therefor.
2. Description of the Related Art
In an ink jet printer which supplies ink from an ink tank to a print head to perform printing and recovers ink not used for printing into the ink tank, control of the properties of ink is essential for the stable formation of ink droplets. Particularly for an ink jet printer in which mixing with a nozzle cleaning solvent causes a decrease in the ink concentration, a technique as described in JP-A No. H7(1995)-205448 is used in which the inside of the ink tank is ventilated to accelerate volatilization of such solvent to restore the original ink concentration.
In the ink jet printer as described in JP-A No. H7(1995)-205448, a lot of dust and ink mist may be suspended around the print head and when air is supplied into the print head to air-purge it in order to remove such dust and ink mist, an air source for air-purging the print head is required in addition to the air pump used for air purging in the ink tank. The use of such an additional air source leads to a rise in the cost. In addition, when the ink tank is air-purged, exhaust air is forced out of the printer main unit and released to the atmosphere. If ventilation around the printer is insufficient, the solvent concentration may go up, causing the operator to feel uncomfortable.